Linear Equation in One Variable
A linear equation in one variable can be written in the form
Ax + B = C,
Where A, B, and C are real numbers, with A ≠ 0.
A linear equation is also called a first-degree equation since the greatest power on the variable is one. Some examples of equations that are not linear (that is, nonlinear) are
X2 + 3x = 5 , 
= -22, and 
= 6.